Located in southern Maine, the Casco Bay watershed encompasses 985 square miles from the western mountains near Bethel to the coastal waters of Phippsburg and Cape Elizabeth.  The watershed includes 41 of the state’s fastest growing communities and approximately 25% of its population, including the  largest metropolitan area – Portland.  In addition, the watershed boasts 785 islands, islets, and exposed ledges, and more than 1,356 miles of rivers and streams.  

Five sub-watersheds comprise the Casco Bay watershed, including the Sebago Lake, Presumpscot River, Royal River, Fore River, and Coastal watersheds.   Twelve significant lake and river systems feed the Bay – including Sebago Lake, Greater Portland’s drinking water source – and three major freshwater tributaries: the Fore, Presumpscot, and Royal Rivers.